1. Field of the Invention
The present invention relates to a method of cleaning a semiconductor device fabrication apparatus. More particularly, the present invention relates to a method of cleaning the interior of a semiconductor device fabrication apparatus of by-products produced as the result of forming a conductive layer on a semiconductor substrate.
2. Description of the Related Art
Recently, due to the rapid development of information communication technology and the widespread use of data storage media, such as computers, demands have increased for semiconductor devices that operate faster and have a larger data storage capacity. Accordingly, there is a growing trend to improve semiconductor device fabrication technology with the aim of increasing the integration density, reliability and response speed of the devices.
In general, a semiconductor device can be made more highly integrated if a dielectric material formed on a semiconductor substrate of the device can be made thinner. However, semiconductor devices become more susceptible to leakage current the thinner the dielectric material becomes. Accordingly, a thin dielectric layer may compromise the operational reliability of the semiconductor device.
Metal oxides, e.g., Al2O3, are typically employed as dielectric materials of semiconductor devices. Research into metal oxides having a high dielectric constant is actively under way to provide a solution to the leakage current problem. Specifically, attempts are being made to use a Zr oxide or an Hf oxide as a dielectric material capable of allowing highly integrated semiconductor devices to operate in a reliable manner.
However, the use of a Zr oxide or an Hf oxide as a dielectric material of a semiconductor device presents several problems. These will now be described more fully with reference to FIGS. 1A through 1D. In a conventional semiconductor device fabrication apparatus, as shown in FIG. 1A, a semiconductor substrate 2 having an Hf oxide (HfO2) layer is disposed on a heater 1, and a conductive layer, e.g., a TiN layer, is formed on the HfO2 layer using NH3 and TiCl4 as source gases. Referring to FIG. 1B, although the semiconductor substrate 2 is then transferred outside the apparatus, oxygen components remain on a region of the heater 1 where they react with the source gases or Hf ions remaining in the apparatus. As a result, a byproduct layer 3 containing HfN and an Hf oxide is undesirably formed on the heater 1. Likewise, in the case of forming a conductive layer, e.g., a TiN layer, on a Zr oxide (ZrO2) layer using NH3 and TiCl4 as source gases, a layer of byproduct containing ZrN and Zr oxide is formed on the heater 1.
As shown in FIG. 1C, the process of forming a conductive layer on a semiconductor substrate 2 having an Hf oxide or a Zr oxide is repeated Consequently, the thickness of the layer 3 comprising HfN and an Hf oxide (or ZrN and a Zr oxide) increases on the region of the heater 1 dedicated to support the semiconductor substrate 2.
Japanese Patent Laid-open Publication No. 2003-203907 suggests using a chemical vapor deposition (CVD)-based cleaning process to remove the byproduct layer 3 from the heater 1. However, practice has shown that CVD cannot completely remove the layer 3. Furthermore, removing the byproduct layer 3 involves opening the semiconductor device fabrication apparatus periodically. This results in downtime that decreases the productivity of the semiconductor device fabrication process.